Development of Aluminum Nitride Infrared Window by HVPE

TDI proposes to develop aluminium nitride infrared window material using hydride vapor phase epitaxy (HVPE) of AlN. The HVPE technique is a well-established, relatively cheap method to grow thick layers of GaN on sapphire and silicon carbide substrates. This epitaxial method provides high growth rate sufficient to obtain quasi bulk material. Our recent experiments show that high quality, thick AlN epitaxial layers can be grown by HVPE. AlN free-standing platelets have been obtained. Preliminary experiments indicate that grown AlN is transparent in the wavelength region from 2 to 6 microns. These results open the opportunity to develop large area AlN high quality infrared window material. The goal of the Phase I is to prove the concept and demonstrate free-standing 1 mm thick AlN platelets with a lateral size at least 15x15 sq.mm. We will measure physical properties of grown AlN, including optical absorption in the wavelength region from 1 to 10 microns. Test samples will be delivered. In the Phase II, we will focus on the development of multi-wafer HVPE growth process for AlN deposition. We plan to grow and characterise 25 - 50 mm diameter, 2.5 mm thick AlN disks having high crystal quality and absorption coefficient < 0.1 per centimetres at 4 microns.